Raising the roof on gardening

Published May 28, 2013

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Durban - Living green roofs absorb carbon dioxide, provide insulation, absorb run-off and noise and reduce the “heat island” effect of built-up areas. They also beautify urban environments.

Local expert and consultant to the eThekwini Municipality, Clive Greenstone, is working towards his PhD at the School of Built Environment and Development Studies at the University of KwaZulu-Natal.

His thesis has the title “Creating resilient urban ecological systems in the eThekwini Municipality: the role of green roofs and rooftop gardens”.

He says he first became interested in rooftop gardens about eight years ago during his honours year and under the supervision of Dr Harald Witt, who is now his PhD supervisor.

“With regards to furthering my horticultural knowledge, I have had numerous mentors, particularly Mike Hickman and Geoff Nichols.”

Greenstone believes that virtually any surface can be greened.

“The structural loading capacity of the surface must be investigated before any form of installation. That said, there are numerous materials and techniques available that allow for ease of installation.”

“However, over time, the majority of green roofs fail. You may want to call in a professional, as each roof is context-specific, for example, location, height, climatic factors, rainfall, sunshine, shade and wind accessibility all play a part. There are specific processes, such as drainage systems, green roof materials, specialised growing mediums and plant species combinations that must be adhered to. It must also be noted that not all indigenous plants can handle the tough growing conditions.”

Greenstone says that with marked temperature differences, creating productive natural ecosystems on urban rooftops is paramount to green roof longevity and future city identities.

It may sound difficult, but the benefits are well worth the effort.

“Green roofs and rooftop gardens are able to better utilise stormwater run-off. The plants absorb air pollutants and dust. They help to reduce the urban heat island effect – the higher-temperature ‘dome’ created over an urban or industrial area by hot air layers forming at building-top or chimney-top level. And when designed and installed correctly, they increase urban biodiversity through ecosystem creation and habitats for wildlife.”

Not to mention that they are attractive.

Greenstone adds that gardens have been found to promote health benefits for humans.

“It has been shown that green roofs and roof gardens in and on top of hospitals have an immediate effect on human well-being. They create an atmosphere of transition from despair to hope, as well as promoting an opportunity for exercise, and an appreciation of fauna attracted to the gardens.” - The Mercury

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